The term decorative panel in the sense of the invention means wall, ceiling or floor panels comprising a decoration applied onto a carrier plate. Decorative panels are used in a variety of ways both in the field of interior design of rooms and for decorative cladding of buildings, for example in exhibition stand construction. One of the most common application fields of decorative panels is their use as a floor covering. Herein, the decorative panels often comprise a decoration intended to replicate a natural material.
Examples of such replicated natural materials are wood species such as maple, oak, birch, cherry, ash, walnut, chestnut, wenge or even exotic woods such as Panga Panga, mahogany, bamboo and bubinga. In addition, often natural materials such as stone surfaces or ceramic surfaces are replicated.
Heretofore, such decorative panels have often been produced as laminates in which a decorative paper preprinted with a desired decoration is applied onto a carrier plate and, in turn, a so-called overlay is applied onto the decorative paper. After optionally a backing paper has been applied to the side of the carrier plate opposite to the decorative paper, the laminate structure obtained is fixedly bonded together by use of appropriate pressure and/or heat-activated adhesives.
Dependent on the desired area of application of the decorative panels they can be made of different materials. In particular, the material of the carrier can be chosen depending on the area of application. Thus, the carrier may for example consist of a wood-based material, provided that the decorative panels are not exposed to excessive moisture or weather conditions. If the panel on the other hand is to be used for example in wet rooms or outdoors the carrier may for example consist of a plastic material.
Examples of plastic materials which may be used for the production of corresponding panels are thermoplastic materials such as polyvinyl chloride, polyolefines (such as polyethylene (PE), polypropylene (PP)), polyamides (PA), polyurethanes (PU), polystyrene (PS), acrylonitril butadiene styrene (ABS), polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyether ether ketone (PEEK) or mixtures or co-polymerizates thereof. The plastic materials can include common fillers, such as calcium carbonate (chalk), aluminum oxide, silicagel, quartz powder, wood flour, gypsum. In addition they can be coloured in a known way.
For applying a decoration onto the carrier plate or a plate-shaped carrier it is known to apply a decorative paper printed with a corresponding decoration onto the plate-shaped carrier, for example by means of a resin layer previously applied onto the plate-shaped carrier as a bonding agent. Moreover, it is known to provide decorative panels with a decoration by means of a so-called direct printing process.
The term “direct printing” in the sense of the invention means the application of a decoration directly onto the carrier of a panel or onto an unprinted fiber material layer applied to the carrier. In contrast to the conventional methods in which a decorative layer previously printed with a desired decoration is applied onto the carrier, in direct printing the decoration is printed directly in the course of the panel manufacturing process. Here, different printing techniques such as flexographic printing, offset printing or screen printing may be used. In particular digital printing techniques such as inkjet processes or laser printing can be used.
In the sense of the invention the term fiber materials means materials such as paper and non-woven fabrics on the basis of plant, animal, mineral or even synthetic fibers as well as cardboards. Examples are fiber materials on the basis of plant fibers and, in addition to papers and non-woven fabrics made of cellulose fibers, boards made of biomass such as straw, maize straw, bamboo, leaves, algae extracts, hemp, cotton or oil palm fibers. Examples of animal fiber materials are keratin-based materials such as wool or horsehair. Examples of mineral fiber materials are mineral wool or glass wool.
For protecting the applied decoration layer normally wearing or top layers are applied on top of the decorative layer. A wearing and/or top layer in the sense of the invention is a layer applied as an outer border which in particular protects the decorative layer from wear or damage caused by dirt, moisture or mechanical impacts, such as abrasion.
It is often provided that in such wearing or top layers a surface structure matching with the decoration is produced. A surface structure matching with the decoration means that the surface of the decorative panel has a haptically perceivable structure which with respect to its shape and pattern corresponds to the applied decoration in order to achieve a reproduction of a natural material as close to the original as possible even with respect to the haptic.
In order to extend the areas of application of said decorative panels in particular in wet rooms or outdoors in addition to carriers on the basis of wood-based materials as a material of the plate-shaped carrier also plastic materials are recently increasingly used as a material for such carriers. Such panels are known, for example, from the international patent application WO 2010/023042 A1. A disadvantage of these plate-shaped carriers is that the plastic materials used for the production of the plate-shaped carriers on the one hand are mainly derived from mineral oils, the limited resources of which contributes significantly to the costs, and on the other hand such mineral oil based products are often assessed as critical. Moreover, plastic materials hitherto used for the plate-shaped carriers, such as in particular polyvinyl chloride (PVC) are increasingly getting into the focus of public criticism, since they may involve a relevant problem potential from an ecological perspective. Thus, for example, for the production of soft PVC plasticizers, e.g. from the group of phthalates, have to be added in an amount of 20-30 wt.-% in order to ensure the desired elasticity of the PVC material. Such additives, however, are considered as critical in the course of recent legal regulations and this is the reason why it is tried to avoid the use of such substances.